Dual mode I.V. infusion device with distal sensor

ABSTRACT

An improved dual mode peristaltic device is provided for infusing I.V. solutions to a patient through an I.V. tube. In a first mode of operation, the device functions as a peristaltic pump and in the second mode of operation it functions like a controller. Included in the device and associated with the I.V. tube is a pressure sensing strain gauge assembly that monitors dimensional changes in the outer diameter of the I.V. tube as an indication of fluid pressure changes in the tube. The strain gauge assembly is positioned relative to the device&#39;s peristaltic means to alternately monitor fluid pressure in a patent I.V. tube upstream and downstream from the gauge assembly. A pair of stationary fingers surround the strain gauge assembly to isolate it from the pulsitile nature of the peristaltic action of the device. In the first mode (pump mode), the device is programmed to alarm and cease operation when fluid pressure downstream from the gauge assembly reaches a preselected value. In the second mode (controller mode), the device is programmed to alarm and cease operation when there is no differential between fluid pressure upstream and downstream from the gauge assembly.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of my prior application for a"Dual Mode I.V. Infusion Device," Ser. No. 801,987 filed Nov. 26, 1985now U.S. Pat. No. 4,617,014 issued Oct. 14, 1986. This invention relatesgenerally to a device used for the infusion of medical solutions to apatient. More specifically, the present invention relates to a dual modedevice which can alternately function either as an infusion pump or as acontroller. This invention is particularly though not exclusively,useful for the intranveous infusion of medical solutions to a patientunder conditions where the flexibility of a dual mode capability isdesired.

DESCRIPTION OF THE PRIOR ART

Many medical devices have been proposed to infuse medical solutions to apatient. Indeed, in recent years the use of such devices has gained wideacceptance. Consequently, a variety of medical solution infusion deviceshave been suggested for use in numerous medical and surgicalapplications. Typically, these devices can be grouped into either of twocategories. The first group is generically referred to as controllersand the second group is referred to as pumps. Examples of medicaldevices in each category are so numerous it is not deemed instructive tolist them here.

It is instructive, however, to understand the basic difference between apump and a controller. Fundamentally, controllers are medical deviceswhich connect with a gravity feed I.V. administration line for thepurpose of controlling the rate of fluid flow through the line. In I.V.administration systems where controllers are used, the fluid pressurefor delivering fluid to the patient is dependent solely on the systemhead height. In other words, fluid pressure in the system depends on thebottle height of the fluid source above the patient. In such a system,the function of the controller is to constrict the tubing of theadministration set to regulate the rate of fluid flow through thetubing. The controller does not contribute to the fluid pressure.

Several advantages are obtained by using controllers. Firstly, asmentioned above, they provide a means for controlling the rate of fluidflow through a gravity system. Secondly, controllers are generallyperceived by hospital personnel as being safe since they operate at lowfluid pressures and thus are not apt to cause tissue damage to thepatient at the injection site. Further, they are easily understood andrather simple to use. An example of a controller which is widely usedthroughout the medical profession at the present time is disclosed inU.S. Pat. No. 4,300,552 to Cannon which is assigned to the same assigneeas the present invention.

Unlike controllers, medical devices in the second group, i.e. pumps,provide a mechanical action on fluid within the system to establish anartificial fluid for the system. The medical devices properly groupedinto this category are of several types and include, but are notnecessarily limited to, cassette-type pumps, syringe pumps, diaphragmpumps and peristaltic pumps. As should be expected, the use of pumps forthe infusion of medical solutions provides certain advantages which arenot attainable by a controller. Importantly, these advantages may bevery necessary in a particular medical application. For example, an I.V.pump is better suited than is a controller to (a) overcome resistance tofluid flow caused by small gauge catheters and small gauge I.V. tubing;(b) infuse the more viscous fluids; (c) overcome in vivo resistance; (d)achieve higher fluid flow rates; and (e) provide perceptively a higherdegree of volumetric accuracy. These advantages are due, in large part,to the fact that pumps exert a mechanical pressure on the fluid prior tothe infusion of the fluid into the patient whereas controllers depend ongravity to move fluid through the system. An example of an I.V. pump isdisclosed in U.S. Pat. No. 3,985,133 to Jenkins which is assigned to thesame assignee as the present invention.

Regardless of the type of I.V. infusion system used, it is widelyrecognized that the ability to monitor fluid pressure in the fluid lineis a distinct advantage for the safe operation of any I.V.administration system. Specifically, but regardless whether it be a pumpor a controller, where electro-mechanical medical devices are employedand fluid pressure within the line can be determined, the medical devicecan be programmed to react to changes in the fluid pressure. Forexample, in a pumping system, if the detected fluid pressure of the linerises above some predetermined level, an occlusion in the system may beindicated and it would be advantageous to have the medical device ceaseoperation. Likewise, with a controller, if the detected fluid pressurerises above a predetermined level, an occlusion may be indicated and theinfusion should be stopped.

The importance of knowing the fluid pressure in an I.V. administrationsystem is underscored by the fact that several proposals have been madefor devices which monitor physical characteristics of the fluid flowline and correlate changes in these characteristics to changes in fluidpressure. In one such system, as disclosed in U.S. Pat. No. 4,526,574 toPekkarinen, a differential occlusion sensing apparatus is disclosedwhich monitors the location of a portion of the I.V. tube and translatesvariations of the location measurement from a base location into a fluidpressure indication. In another system, as disclosed in U.S. Pat. No.Re. 31,315 to Jenkins et al. and assigned to same assignee as for thepresent invention, the fluctuations of a diaphragm in fluidcommunication with the fluid flow are monitored as being indicative ofthe fluid pressure level.

It will be appreciated that in a hospital environment, circumstances candictate whether there is a need for a pump or a controller. Presently,depending on the situation, hospital personnel must obtain a pump forsituations wherein a pump is required and obtain a controller for thosesituations requiring a controller. Not only does this require theavailability of two separate medical devices, it also requires knowledgeand skills for their separate set up and operation. Until the presentinvention, there has been no single unitary medical device capable ofobtaining the desired advantage of either a pump or a controller.

In light of the above, the present invention recognizes the separate anddistinct advantages obtainable by using pumps or controllers and thebenefits to be derived in I.V. administration systems which have fluidpressure monitoring capabilities. Specifically, the present inventionrecognizes the desirability of obtaining the combined advantages of apump and a controller from a single universal device which, depending onthe desires of the operator, can function either as an I.V. pump or likea controller and which thereby obtains the desired advantage of theparticular mode of operation. In accordance with the present invention,this dual mode capability is made possible by providing the system witha fluid pressure sensor which permits modal operation in compliance withdetectable pressure limitations. Also, with electronic controls to ceaseoperation of the system whenever elevated fluid pressure indicates anocclusion, the dual mode medical device of the present invention can besafely operated regardless of its selected mode of operation.Specifically, where a peristaltic pump is used, this inventionrecognizes that the necessary fluid pressure information for a dual modedevice can be obtained by alternately monitoring fluid pressure in thepatent I.V. tube upstream and downstream from the moving zone ofocclusion.

Accordingly, one object of the present invention is to provide a singlemedical device which can be switched to function either as a peristalticpump or like a controller. Another object of the present invention is toprovide a dual mode device which is directly operable on an I.V. tubefor the infusion of medical solutions to a patient and is thusnon-invasive of the fluid line. It is still another object of thepresent invention to provide a cost effective, relatively accurate andeasy to use medical device for the infusion of medical solutions to apatient.

SUMMARY OF THE INVENTION

The preferred embodiment of the present invention comprises a medicaldevice for infusing I.V. fluids to a patient through an I.V. tube inwhich the device is operatively engageable with a portion of the I.V.tube. Upon engagement of the device with the I.V. tube, a peristalticmeans in the device is positioned against a portion of the I.V. tube tosequentially squeeze the I.V. tube and produce a moving zone ofocclusion along the tube for pumping fluid therethrough in accordancewith the peristaltic action. The device further includes a strain gaugeassembly which is positioned against the I.V. tube and operativelyassociated with the peristaltic pumping means so as to be able tomonitor fluid pressure downstream and upstream of the occlusionrespectively before and after the occlusion has passed the point atwhich the gauge assembly is operatively associated with the I.V. tube.For the improved embodiment of the present invention, the strain gaugeassembly is located near the distal end of the peristaltic means tomaximize the time the gauge monitors fluid pressure downstream from theocclusion. The improved embodiment also includes a pair of stationaryfingers with one finger disposed upstream and adjacent to the straingauge assembly and the other finger disposed downstream and adjacent tothe strain gauge assembly to isolate the strain gauge assembly from theaction of the peristaltic means. The present invention further includesmeans to switch the device between one mode of operation wherein thestrain gauge assembly monitors only the fluid pressure downstream fromthe occlusion (the pumping mode) and another mode wherein the straingauge assembly is able to alternately monitor the fluid pressure in theI.V. line upstream and downstream from the occlusion (the controllermode).

In the first or pumping mode, the device of the present invention isprovided with microprocessor programmed means to alarm and ceaseoperation of the pump whenever the strain gauge assembly indicates thatfluid pressure downstream from the occlusion has reached a preselectedvalue. In the controller mode of operation, the device is microprocessorprogrammed to alarm and/or cease operation when the differential betweenfluid pressure downstream from the peristaltic occlusion and the fluidpressure upstream from the peristaltic occlusion is a null.

The novel features of this invention, as well as the invention itself,will be best understood from the accompanying drawings, taken togetherwith the accompanying description, in which similar reference charactersrefer to similar parts and in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the device in its environment for infusing medicalsolutions from a fluid source to a patient;

FIG. 2 is a cross-sectional view of the peristaltic assembly as seenalong the line 2--2 in FIG. 1 and rotated into the position as shown forclarity;

FIG. 3 is a portion of the peristaltic assembly as shown in FIG. 2 withthe peristaltic action taking place at a different location;

FIG. 4 is a cross-sectional view of a portion of the peristalticassembly as seen along the line 4--4 in FIG. 2;

FIG. 5 is a cross-sectional view of a portion of the peristalticassembly as seen along the line 5--5 in FIG. 2;

FIG. 6 is a cross-sectional view of the strain gauge assembly of theperistaltic assembly as seen along the line 6--6 in FIG. 2;

FIG. 7 is a graph showing periodic variation in fluid pressure as afunction of the peristaltic action of the device;

FIG. 8 is a cross-sectional view of a portion of a peristaltic assemblyof an alternate embodiment of the present invention;

FIG. 9 is a block diagram of the electronic components of the presentinvention;

FIG. 10 is a cross-sectional view of a portion of the peristalticassembly of the improved embodiment of the present invention; and

FIG. 11 is a graph showing periodic variation in fluid pressure as afunction of the peristaltic action of the improved embodiment of thedevice.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIG. 1, a controller/pump generally designated 10is shown in its intended environment. The controller/pump 10 is mountedon I.V. pole 12 in a manner well known in the art. An I.V. fluid source14 is hung from the I.V. pole 12 as shown in FIG. 1, and an I.V. tube 16is connected in fluid communication with fluid source 14 and operativelyconnected with controller/pump 10 in a manner as generally shown inFIG. 1. Downstream from its point of engagement with controller/pump 10,I.V. tube 16 is coupled with patient 20 for the infusion of medicalsolutions to the patient 20.

FIG. 2 is a cross-sectional view of the peristaltic assembly, generallydesignated 22, which is shown here in isolation from controller/pump 10for purposes of clarity. As shown in FIG. 2, peristaltic assembly 22includes a motor 24 which is preferably a stepper motor but may be ofany type well known in the relevant art. A drive shaft 26 is rotated bythe stepper motor 24 and is secured to an attachment 28 by any meanswell known in the art in a manner which permits the rotation ofattachment 28 to move a drive pulley 30. Drive pulley 30 is connected inoperative engagement with an attachment 32 that is in turn secured tocam shaft 34 by any means well known in the art. The cam shaft 34 issupported on peristaltic assembly 22 by a bushing 36 and a bushing 38.Fixed on cam shaft 34 at predetermined locations along the axis of thecam shaft 34 is a series of cam lobes 40. As will be appreciated bythose skilled in the pertinent art, cam lobes 40 are eccentricallymounted on cam shaft 34 in a helical pattern along the axis of cam shaft34 in a manner which will create a peristaltic action by the movement ofthe fingers 42. The movement of the individual fingers 42 will be bestappreciated by reference to FIG. 4.

Referring to FIG. 4, it is seen that each of the individual fingers 42are formed with an aperture 58 to receive an individual cam lobe 40therein. Each finger 42 is mounted in housing 48 of the peristalticassembly 22 in a manner which provides for movement of the finger 42 ina direction substantially perpendicular to the longitudinal axis of camshaft 34. It will be appreciated with reference to FIG. 4 that thehousing 48 comprises a side 50a and a side 50b which are formed withbaffles 52a and 52b to create gooves 54a and 54b that maintain thealignment of finger 42 relative to cam shaft 34. A cross-reference ofFIG. 4 with FIG. 5 shows that the rotation of cam shaft 34 causes aconsequent rotation of the eccentrically mounted cam lobe 40 which, inturn, urges against respective portions of the aperture 58 to cause areciprocal vertical motion of finger 42 within the housing 48. Referringback to FIG. 2 or FIG. 3, it can be appreciated by the skilled artisanthat cam lobes 40 can be sequentially located along cam shaft 34 in ahelical manner. With cam lobes 40 so located, rotation of cam shaft 34causes fingers 42 to move in a direction substantially perpendicular tothe axis of cam shaft 34 and in a manner which will provide aperistaltic action by the concerted movement of the various fingers 42.

Again referring to FIG. 2, it will be seen that the I.V. tube 16 can beplaced in operative contact with the peristaltic assembly 22 by locationof the respective fitments 60 and 62 into the base 84 of peristalticassembly 22. As shown in FIG. 2, a pumping section 18 of I.V. tube 16can be defined between fitments 60 and 62. This particular pumpingsection 18 may be made of the same material as I.V. tube 16. However, inthe preferred embodiment, the pumping section 18 comprises a veryflexible and compressible elastomeric material. Such elastomer may be asilicone rubber of the type identified as RX 50 and manufactured by DowCorning. It will also be appreciated by reference to FIG. 2 or FIG. 3that once I.V. tube 16 and its associated pumping section 18 have beenmounted on peristaltic assembly 22, a door 82 can be closed to provide aplaten 46 that is positioned against pumping section 18, as shown, andwhich provides resistance against the motion of the fingers 42 as theyurge on pumping section 18. Also shown in FIG. 2 and FIG. 3, a membrane56 is located between the ends 94 of fingers 42 and pumping section 18to separate fingers 42 from pumping section 18 and provide for theisolation of I.V. tube 16 and pumping section 18 from the peristalticassembly 22. Again, it will be appreciated by the skilled artisan thatdepending upon cam shaft rotation θ and the helical orientation of camlobes 40 along cam shaft 34, a particular finger 42 can be caused tourge against pumping section 18. Further, it will be appreciated thateach complete revolution of cam shaft 34 causes a sequential progressionof the fingers 42 to urge against pumping section 18 and generate aperistaltic action against pumping section 18. The specific action offingers 42 on pumping section 18 is best seen by cross-referencing FIG.4 and FIG. 5. These figures respectively show the action of a finger 42that causes an occlusion on pumping section 18 and a patentcy conditionon pumping section 18. It will be appreciated by the skilled artisanthat a moving zone of occlusion is created as cam shaft 34 is rotated tocause a sequential urging of fingers 42 against pumping section 18.

The preferred embodiment of the present invention also includes a gaugeassembly 44 which is associated with peristaltic assembly 22 and mountedwith respect to the fingers 42 of peristaltic assembly 22 as generallyshown in FIG. 2 and FIG. 3. An improved embodiment of the presentinvention associates the gauge assembly 44 with peristaltic assembly 44near the distal or downstream end of the peristaltic assembly 44 asgenerally shown in FIG. 10. A more detailed description of the gaugeassembly 44 can be obtained with reference to FIG. 6.

In FIG. 6 the gauge assembly 44 is shown in cross-section and is seen toinclude a mounting block 70 on which is fixedly mounted a cantileveredstrain beam 68. On the surface of cantilevered strain beam 68, but notshown in FIG. 6, is a strain gauge. The entire assembly which comprisesblock 70, strain beam 68 and strain gauge 108 is of a type similar tomodel No. X1680 manufactured by Transducers, Inc., 14030 Bolsa Lane,Cerritos, Calif. 90701. Extending from mounting block 70, as shown inFIG. 6, is a travel limiter 72. Mounted on the opposite side of thecantilevered strain beam 68 opposite from the travel limiter 72 is aprotective extension 74. Fixedly attached to cantilevered strain beam 68at the end opposite from its connection with mounting block 70 is apressure transmitting member 76 which is positioned to physicallyconnect the end of cantilevered strain beam 68 with pumping section 18upon engagement of the I.V. tube 16 with the controller/pump 10. Alsoconnected with cantilevered strain beam 68 is an electrical junctionblock 78 that provides a connection for the electrical circuitry fromthe strain gauge (not shown). Electrical wiring 80 provides furtherconnection between the cantilevered strain beam 68 and the electroniccomponents of the present invention for a purpose to be subsequentlydiscussed.

As will be appreciated by reference to FIG. 6, upon engagement of I.V.tube 16 with controller/pump 10, a portion of pumping section 18 ispositioned between platen 46 of door 82 and the pressure transmittingmember 76 which is directly and physically connected with thecantilevered strain beam 68. As also seen in FIG. 6 and previouslydiscussed, a membrane 56 can be placed between the pressure transmittingmember 76 and pumping section 18 for the purposes of isolating theperistaltic mechanism from the functional I.V. administration set beingused in conjunction with the controller/pump 10 and protecting theinterior of controller/pump 10 from tampering and contaminants.

Referring now to FIG. 9, the electronic componentry of thecontroller/pump 10 is set forth in block diagram form. As seen in FIG.9, this componentry includes a microprocessor 100 which may be of anytype well known in the pertinent art. For example, a microprocessor asmanufactured by Intel Corporation, model No. 8032, can be used for thepurposes of the present invention. Electrically connected tomicroprocessor 100 is an EPROM 102 which provides code information forthe operation of microprocessor 100. Also electrically connected tomicroprocessor 100 is a RAM 104 which has the capacity to store andpreserve various system parameters during a power condition. It will beappreciated by the skilled artisan that EPROM 102 and RAM 104 are oftypes well known in the pertinent art. Examples of these componentswhich will satisfy the requirements of the present invention arerespectively a model No. D27512 manufactured by Intel and a model No.HM6116 manufactured by Hitachi. Also electrically connected tomicroprocessor 100 is a watchdog circuit 106 which provides for systemintegrity. More specifically, watchdog circuitry 106 insures thatstepper motor 24 and microprocessor 100 are functioning correctly.Additionally, watchdog circuit 106 provides a reset capability for thesystem and provides means for stopping the operation of the system.

Also shown in FIG. 9 is a strain gauge 108. It will be recalled thatstrain gauge 108 was not shown in the earlier description of gaugeassembly 44. As can now be more easily appreciated, it is the straingauge 108 which is electrically attached to cantilevered strain beam 68.With this attachment the flexures of cantilevered strain beam 68 whichare caused by the movement of pressure transmitting member 76 inresponse to variations in the outer diameter of pumping section 18 willbe sensed by the strain gauge 108. Electronically, it can be appreciatedthat the analog voltage measurements obtained from strain gauge 108represent a voltage which requires conversion by an A/D converter 110before it is electrically compatible with microprocessor 100. As shownin FIG. 9, the ciruitry for this electrical connection is provided.

Also shown in FIG. 9 is the electrical relationship of the stepper motor24 with microprocessor 100. As seen in FIG. 9, it is necessary forstepper motor 24 to be directly connected with motor controller 112. Amctor sensor 114 (also generally known as a shaft encoder) is alsodirectly connected with motor controller 112 and generates electronicsignals which correlate the running of motor controller 112 with theposition of cam shaft 34 as indicated by cam shaft rotational positionθ. A keyboard/display 116 is provided to permit operator access to theelectronic componentry of the controller/pump 10. Throughkeyboard/display 116 an operator is able to key in the various systemparameters which are necessary to operate the controller/pump 10. It isthrough keyboard/display 116 that an operator selects the mode ofoperation for controller/pump 10 and establishes the preselected valuesfor fluid pressure limitations in the selected mode of operation.Together with input from keyboard/display 116, microprocessor 100operates in accordance with code from EPROM 102 and input from RAM 104.One result obtained from this arrangement is that a reading on straingauge 108 can be read by microprocessor 100 in accordance with a presetprogram.

As envisioned in the present invention, motor sensor 114 monitors camshaft position θ. Based on cam shaft position θ, input from motor sensor114, motor controller 112 provides signals to microprocessor 100 whichare compared and timed according to a prepared program. Microprocessor100 also receives signals from A/D converter 110 which have beengenerated by strain gauge 108 in response to movements of cantileveredstrain beam assembly 68. Recall that readings from strain gauge assembly64 are correlated to fluid pressure readings in I.V. tube 16.Microprocessor 100 is preprogrammed to accept fluid pressure readingsfrom strain gauge 108 at selected times which depend on cam shaftposition θ as indicated by motor sensor 114. Further, microprocessor 100is preprogrammed to compare the fluid pressure readings from straingauge 108 with the modal fluid pressure limitations established by theoperator. Stepper motor 24 is then run in accordance with programmedsignals from microprocessor 100 to operate the structure ofcontroller/pump 10 as discussed elsewhere in this disclosure.

Further in FIG. 9, it is shown that various peripheral electricalcomponents may be added to the controller/pump 10 to expand itscapabilities. Examples of peripheral equipment that could be includedwithin a system for controller/pump 10 is shown in FIG. 9 andconnections between these peripheral componentry and microprocessor 100is accomplished by way of an I/O expander 118. As seen in FIG. 9, anair-in-line detector (AIL) 120, an empty bottle detector (EBD) 122 and adoor sensor 128 are examples of peripheral equipment which could beincorporated into the controller/pump 10 system. Also shown in FIG. 9and electrically connected to I/O expander 118 is an alarm 124 and apower off switch 126. In all respects the electronic componentry of thepresent invention are made from electronic elements which are well knownin the pertinent art and are commercially available. It will beunderstood and appreciated that the electronic componentry system as setforth in FIG. 9 is merely illustrative and that its purpose is toprovide a background which is electronically compatible with thestructural integrity and the cooperation of structure of thecontroller/pump 10 of the present invention

FIG. 8 shows an alternate embodiment of the present invention whichemploys two gauge assemblies as opposed to the single gauge assembly 44disclosed for the preferred embodiment. In the alternate embodiment, agauge assembly 64 is positioned at the upstream end of the peristalticfingers 42 and a second gauge assembly 66 is positioned at thedownstream end of the peristaltic fingers 42. In all respects, gaugeassemblies 64 and 66 are similar in structure to that as disclosed forgauge assembly 44 and incorporate all of the elements previouslydescribed for gauge assembly 44. It will be understood that electroniccomponentry for the alternate embodiment need not include provision foralternately reading gauge assemblies 64 and 66. Instead, continuousreadings may be taken and used in a logic sequence similar to that forthe preferred embodiment.

FIG. 10 shows an improved embodiment of the present invention in which asingle gauge assembly 44 is located near the distal or downstream end ofthe peristaltic assembly. This location accomplishes two purposes.First, with gauge assembly 44 near the distal end of peristalticassembly 22, gauge assembly 44 acts as a sensor which remains downstreamfrom the occlusion during a greater portion of the cycle of rotation θfor cam shaft 34. Thus, gauge assembly 44 monitors or senses the morecritical fluid pressure in the IV line between the occlusion and thepatient for a longer period of time. Second, this positioning causesgauge assembly 44 to not monitor downstream pressure at a time whenthere is only low incremental flow downstream from controller/pump 10 tothe patient. Thus, the distal positioning of gauge assembly 44 minimizesboth the time and the amount of unmonitored pressurized fluid flow tothe patient from controller/pump 10.

The improved embodiment also includes stationary fingers 130 and 132which are adjacent gauge assembly 44 and respectively located upstreamand downstream from gauge assembly 44. As best seen in FIG. 10,stationary fingers 130 and 132 urge against pumping section 18 but donot cause an occlusion of the section 18. Instead, fingers 130 and 132remain a predetermined fixed distance from platen 46 to allow fluid flowthrough section 18 while isolating gauge assembly 44 from the effects ofthe peristaltic action of fingers 42. Stationary fingers 130 and 32 maybe fixedly attached to peristaltic assembly 22 by any means well knownin the art.

OPERATION

In its operation controller/pump 10 is placed in operative engagementwith an I.V. tube 16. This is done by positioning I.V. tube 16 againstbase 84 of peristaltic assembly 22 as shown in FIG. 2. With tube 16 inthis position, the fitments 60 and 62 are operatively engaged with base84. As discussed previously, the portion of I.V. tube 16 that is placedagainst membrane 56 and in operative engagement with controller/pump 10is preferably a flexible and compressible pumping section 18.

Once I.V. tube 16 with its pumping section 18 have been engaged withcontroller/pump 10, the door 82 is closed. The closure of door 82 causesplaten 46 to come in contact with pumping section 18 and enclose pumpingsection 18 between platen and membrane 56.

Activation of stepper motor 24 causes rotation of drive shaft 26 in amanner that causes drive pulley 30 to rotate cam shaft 34. The actualpositioning of cam shaft 34 is represented by cam shaft rotation θ. Aswill be appreciated by those skilled in the art, a complete revoluationof cam shaft 34 will cause cam lobes 40 to reciprocate fingers 42substantially perpendicular to the axis of pumping section 18. Due tothe helical configuration of cam lobes 40 on cam shaft 34, fingers 42urge against pumping section 18 to create a moving zone of occlusionalong the length of pumping section 18 during each revolution of camshaft 34. For example, an occlusion, such as the one represented in FIG.2 by the character A, is caused to move along the length of pumpingsection 18 and create a peristaltic pumping action.

During operation of the peristaltic assembly 22, it will be appreciatedby reference to FIG. 6 that gauge assembly 44 can be positioned todetermine dimensional differences in the outer diameter of pumpingsection 18. As seen in FIG. 6, pumping section 18 is located directlybetween platen 46 and membrane 56. During the pumping of fluid throughpumping section 18, the outer diameter of pumping section 18 will vary,dependent upon the fluid pressure within pumping section 18. Thisvariation in pressure will cause a consequent variation in the distancebetween membrane 56 and platen 46 on respectively opposite sides of thecenter portion of pumping section 18. It will be appreciated by thoseskilled in the pertinent art that this change in dimension can becorrelated to changes in the fluid pressure within the pumping section18. As will be further appreciated by those skilled in the art, avariation in the outer diameter of pumping section 18 and the consequentchange in distance between membrane 56 and platen 46 will cause a motionof pressure transmitting member 76 generally in an up and down directionas indicated by the arrow 96. Further, it will be appreciated that themovement of pressure transmitting member 76 in a direction as indicatedby arrow 96 will be manifested as a fluctuation of the cantileveredstrain beam 68. With a strain gauge, or strain gauges, (not shown inFIG. 6) mounted on cantilevered strain beam 68, the fluctuations ofcantilevered strain beam 68 can be electronically measured andtransmitted to a microprocessor 100.

It should be recognized that the motion of pressure transmitting member76 in the direction of arrow 96 is limited by the travel limiter 72.This is a safety feature for the controller/pump 10 since travel limiter72 precludes a motion of pressure transmitting member 76 through adistance that could break or permanently bend the cantilevered strainbeam 68. This safety feature is particularly important because itprevents any inadvertent manipulation of pressure transmitting member 76that could damage cantilevered strain beam 68.

As previously indicated, controller/pump 10 can be operated in eitherone of two modes. Operation in the controller simulation mode requiresoperation of the components in a manner as now described. It has beenrecognized that the fluid pressure in I.V. tube 16 will generally varyaccording to the periodic cycles of graph 86 as presented in FIG. 7. Asseen in FIG. 7, the graph 86 depicts variations in fluid pressure P at aset point within I.V. tube 16 as a function of cam shaft rotation θ.Stated differently, for successive revolutions of cam shaft 34, thevariation in fluid pressure P at a particular point will vary in amanner depicted by the graph 86. It has been determined, however, thatwhen gauge assembly 44 is isolated by stationary fingers 130 and 132 andmoved to a distal position relative to peristaltic assembly 22 assubstantially shown in FIG. 10, gauge assembly 44 will observe aperiodic fluctuation of fluid pressure as generally depicted on thegraph 134 in FIG. 11.

Referring back to the structure of controller/pump 10, it is seen thatthe peristaltic assembly 22 as shown in FIG. 2 has been activated to thepoint where cam shaft rotation θ causes a peristaltic finger 42 toocclude pumping section 18 at location A. It has been determined thatduring operation when peristaltic assembly 22 is in this configuration,the fluid pressure in the section of pumping section 18 contacting gaugeassembly 44 corresponds to points 88 on graph 86 in FIG. 7. Further,when peristaltic assembly 22 has moved to cause an occlusion of pumpingsection 18 at point B, as shown in FIG. 3, the fluid pressure in thesection of pumping section 18 contacting gauge assembly 44 correspondswith the points 90 on graph 86 in FIG. 7. The points 92 on graph 86 inFIG. 7 indicate the pressure in the portion of pumping section 18 incontact with gauge assembly 44 during the transition of the occlusionfrom point A, as shown in FIG. 2, to the point B, as shown in FIG. 3.

It will be further appreciated by those skilled in the relevant art thatduring normal operation of the controller/pump 10 in the simulatedcontroller mode, the fluid pressure upstream from the occlusion causedby peristaltic assembly 22 will be dependent upon the height of fluidsource 14. The downstream pressure during such operation, because of theocclusion created on pumping section 18 by peristaltic assembly 22, willbe a value less than the upstream fluid pressure. Specifically, anupstream fluid pressure reading can be made by gauge assembly 44 whenthe occulsion is at point B as shown in FIG. 3, and a downstream fluidpressure reading can be made by gauge assembly 44 when the occlusion isat point A as shown in FIG. 2. Further, it has been found that thedifferential, indicated by the character 98 on graph 86 in FIG. 7,between the upstream pressure indicated at point 88 and the downstreampressure indicated at point 90 will be relatively constant during normaloperation of controller/pump 10. Under these conditions, controller/pump10 will be programmed to rotate cam shaft 34 at an angular velocitywhich will provide the fluid flow rate preselected by the operator.

Since fluid pressure in a controller is normally established by bottleheight, i.e., the height of the fluid source 14 above the patient 20,controller/pump 10 needs to be sensitive to this parameter. Accordingly,for normal operation of controller/pump 10 in the simulated controllermode, any decrease in differential 98 would indicate that the upstreampressure (indicated by point 88) should also be increased to maintain adifferential 98. This can be accomplished very simply by the operatorraising fluid source 14 to increase the hydrostatic pressure in I.V.tube 16 upstream from the occlusion caused by peristaltic assembly 22.It is recognized, however, that there is a limit on the height to whichan operator may be willing to raise the fluid source 14. Consequently,when fluid source 14 has been raised as high as the operator feels issafe and the differential 98 continues to diminish or reaches a null, analarm condition should be dictated. Accordingly, when switched into thecontroller mode, controller/pump 10 should be programmed throughappropriate circuitry shown in FIG. 9 to alarm and cease operation wherethere is no longer a differential 98.

In all important functional respects, the improved embodiment ofcontroller/pump 10, as shown in FIG. 10, operates in the same mannerdescribed above for the embodiment shown in FIGS. 2 and 3. The improvedembodiment, however, provides a more uniform reading of the fluidpressure variations in the IV tube. This will be better appreciated byreferring to FIG. 11 in which the fluid pressure variations in pumpingsection 18 at the location of gauge assembly 44 in the improvedembodiment are shown for several rotations θ of cam shaft 34. Asdepicted by graph 134 in FIG. 11, the region 136 corresponds to thatportion in the revolution of cam shaft rotation θ during which gaugeassembly 44 monitors fluid pressure downstream from the occlusion (i.e.,fluid pressure seen by the patient). As will be appreciated by theskilled artisan, this downstream pressure is generated by theperistaltic action of controller/pump 10. On the other hand, the region138 corresponds to that portion in the revolution of cam shaft rotationθ during which gauge assembly 44 monitors fluid pressure upstream fromthe occlusion (i.e., fluid pressure due to the height of fluid source 14above the occlusion). This pressure is frequently referred to as "bottleheight." FIG. 11 also shows subsequent cycles of cam shaft revolutionsand similar corresponding regions when gauge assembly 44 is monitoringupstream and downstream pressure.

Insofar as the operation of controller/pump 10 in the controller mode isconcerned, it is the difference between the upstream and downstreamfluid pressures that is important. Normally, the upstream fluid pressure(region 138) must be greater than the downstream fluid pressure (region136). This relationship insures that the patient is not subjected to anygreater pressure than would be caused by only "bottle height."Differential 140 may, however, vary somewhat without affectingoperation. For example, if the downstream pressure increases onlyslightly, such as evidenced by the change seen when comparing region 142with region 136, there may be no cause for concern. Such a pressureincrease may be due to some inconsequential crimping of I.V. tube 16 orchange inpatient position. To overcome such a situation, the operatorcan raise fluid source 14 and thereby increase the upstream pressure.The result of raising fluid source 14 is to change upstream pressure toa level as shown in region 144. Of course, there is a limit on "bottleheight." Thus, whenever differential 140 remains a null, despiteattempts to maintain an actual differential 140 by raising fluid source14 to increase "bottle height," a potentially dangerous situation forthe patient is indicated and controller/pump 10 will cease operation ina manner as previously discussed.

It is appreciated that the present invention need not necessarily belimited to the medical field for use in infusing medical solutions topatients. Indeed, a controller/pump according to the present inventionmay be useful in any application wherein pressurized flow of fluids atrelatively low flow rates is desired.

When controller/pump 10 is to be used in the pumping mode, the upstreamfluid pressure in I.V. tube 16 becomes of much less importance. In thismode of operation, cam shaft 34 is caused to rotate with an angularvelocity which will provide a peristaltic action by peristaltic assembly22 in a manner that provides the desired rate of fluid flow. The crucialconsideration in this mode of operation will be the downstream fluidpressure in I.V. tube 16 which may increase to a level that indicates anocclusion downstream from controller/pump 10. Thus, by having theelectronic components of controller/pump 10 monitor the downstreampressure in I.V. tube 16, a condition can be detected wherein thedownstream pressure exceeds some preselected maximum. Such a preselectedmaximum can be established that either indicates a possible occlusion oran otherwise harmful condition for the patent 20. Thus, whencontroller/pump 10 is operating in the pumping mode, the downstreampressure in I.V. tube 16 is monitored and upon reaching a preselectedmaximum, electronic circuitry is programmed to alarm controller/pump 10and cease its operation.

While the particular controller/pump as herein shown and disclosed indetail is fully capable of obtaining the objects and providing theadvantages herein before stated, it is to be understood that it ismerely illustrative of the presently preferred embodiment of theinvention and that no limitations are intended to the details ofconstruction or design herein shown other than as defined in theappended claims.

I claim:
 1. A device for pumping fluids from a fluid source through atube having a compressible pumping section, which device comprises:acase; means for holding a portion of said compressible pumping sectionon said case; peristaltic means mounted on said case and operativelyengaged with said tube to sequentially squeeze said pumping section andproduce at least one moving zone of occlusion along said pumping sectionfor infusing fluids to the patient; a gauge fixedly mounted on said caseand operatively coupled with said pumping section, at a predeterminedlocation thereon, for sensing fluid pressure in said pumping section atsaid location at a first time when said I.V. tube downstream from saidlocation is patent and at a second time when said I.V. tube upstreamfrom said location is patent; a first stationary finger disposedupstream from and adjacent to said gauge; a second stationary fingerdisposed downstream from and adjacent to said gauge; means to determinea pressure differential between said first time and said second time;and means to alarm and cease operation of said device when said pressuredifferential attains a predetermined value.
 2. A device as cited inclaim 1 wherein said peristaltic means is a linear peristaltic pumphaving an upstream end and a downstream end.
 3. A device as cited inclaim 2 wherein said pumping section is made of an elastomeric material.4. A device as cited in claim 3 wherein said gauge is a strain gaugeassociated with said peristaltic means and positioned to engage saidpumping section intermediate said upstream end and said downstream endof said peristaltic means.
 5. A device as cited in claim 4 wherein saidgauge is positioned near the downstream end of said peristaltic means.6. A device as cited in claim 5 further comprising means to selectivelycause said device to alarm and cease operation when the differentialattains a predetermined minimum value.
 7. A device as cited in claim 5further comprising:means for selectively disregarding the fluid pressurein said pumping section at said second time; and means to alarm andcease operation of said device when the fluid pressure at said firsttime attains a predetermined value.
 8. A device for infusing medicalsolutions to a patient which comprises:a fluid source; a compressibletube connecting said fluid source in fluid communication with thepatient; a case having means for engagingly receiving a portion of saidtube therein; means mounted on said case and engageable with saidportion of said tube for generating a moving zone of occlusion thereonto pump fluid from said source to the patient; a gauge mounted on saidcase and operatively associated with said tube to alternately measurethe outside diameter of said tube at a first time when said tubedownstream from said gauge is patent and at a second time when said tubeupstream from said gauge is patent; a first stationary finger disposedupstream from and adjacent to said gauge; a second stationary fingerdisposed downstream from and adjacent to said gauge; means for comparingthe measurement at the first time with the measurement at the secondtime to establish a differential; and means to alarm said device andcease operation when said differential attains a predetermined value. 9.A device as cited in claim 8 wherein said portion of said tube is madeof an elastomeric material.
 10. A device as cited in claim 9 whereinsaid gauge is synchronized with said pumping means to establish thefirst time when said zone of occlusion is upstream from said gauge andto establish the second time when said zone of occlusion is downstreamfrom said gauge.
 11. A device as cited in claim 10 wherein said gauge isa strain gauge.
 12. A device as cited in claim 11 wherein said pumpingmeans is a linear peristaltic pump having a first end and a second end,and said second end is positioned downstream from said first end.
 13. Adevice as cited in claim 12 wherein said gauge is mounted on saidpumping means near said second end.
 14. A device as cited in claim 13wherein said gauge is noninvasive of said tube.
 15. A device as cited inclaim 14 wherein said engaging means is formed having a peripheralportion that comprises a flexible membrane separating said tube fromsaid pumping means.
 16. A device as cited in claim 14 wherein said tubefurther comprises a first fitment and a second fitment to define saidportion of said tube, and said case further comprises a first attachingmeans and a second attaching means respectively engageable with saidfirst and second fitments to engageably receive said tube.
 17. A deviceas cited in claim 15 further comprising means to selectively cause saiddevice to alarm and cease operation when the differential has attained apredetermined minimum value.
 18. A device as cited in claim 16 furthercomprising:means for selectively disregarding the fluid pressure in saidpumping section at said second time; and means to alarm and ceaseoperation of said device when the fluid pressure at said first timeattains a predetermined value.
 19. A method for infusing I.V. medicalfluids from a fluid source to a patient through an I.V. tube having acompressible pumping section which comprises the steps of:A. Engagingsaid pumping section with a device comprising: a case; means for holdinga portion of said compressible pumping section on said case; peristalticmeans mounted on said case and operatively engaged with said tube tosequentially squeeze said pumping section and produce at least onemoving zone of occlusion along said pumping section for infusing fluidsto the patient; B. Monitoring the fluid pressure at a fixed location ofsaid pumping section with a gauge having a first stationary fingerdisposed upstream from and adjacent to said gauge and a secondstationary finger disposed downstream from and adjacent to said gaugebeing operatively coupled with said pumping section for sensing fluidpressure in said pumping section at said location at a first time whensaid I.V. tube downstream from said location is patent and at a secondtime when said I.V. tube upstream from said location is patent; C.Determining a pressure differential between said first time and saidsecond time; and D. Discontinuing the infusion of fluids to the patientwhen said pressure differential attains a predetermined minimum value.20. The method as cited in claim 19 further comprising the steps of:E.selectively disregarding the monitoring of fluid pressure at said secondtime and the determination of said pressure differential; and F.discontinuing infusion of fluids to the patient when said fluid pressureat said first time attains a predetermined value.